I have used the Terminal app on my OS X Yosemite Macbook Pro to SSH to a Linux machine. I have opened "vim" text editor, and want to send the "insert" keypress via SSH to vim, to start editing. Sure, I can hit "i" to start doing that, but I have been using vim for about 97 years, and have taught my fingers to type "insert".
Other stackexchange questions ask about the insert key, and people have had success with fn+m or fn+return. Neither work for me, and I suspect it has something to do with Yosemite or the fact that I am sending the keypress over SSH to a linux remote machine. The fn+m combination simply sends 'm', and the fn+return simply sends a carriage return. Probably the return or m key is being sent over ssh in combination with a function key, and the remote server (Linux) ignores the function key, but recognizes the unmodified key. I think I need the m or return keys to be modified before being transmitted over SSH.